Controlled humidity refrigerator



P 1948. M. e. SHOEMAKER CONTROLLED HUMIDITY REFRIGERATOR 2 Sheets-Sheet1 Filed Feb. 28, 1945 M. G. SHOEMAKER CONTROLLED HUMIDITY REFRIGERATORSept. 21, 1948.

2 Sheets-Sheet 2,

Filed Feb. 28, 1945 Patented Sept. 21, 1948 CONTROLLED HUMIDITYREFRIGERATOR Malcolm G. Shoemaker, Abington,

by mcsne assignments, to Philco Philadelphia, Pa., a corporation vaniaPa" assignor, Corporation, of Pennsyl- Application February 28, 1945,Serial No. 580,109

Claims.

This invention has to do with refrigeration apparatus and, moreparticularly, is concerned with controlling the moisture content of airwithin the food storage compartment of a refrigerator.

With reference to the present invention, it should be borne in mind thatit is desirable to provide a so-called moist-cold compartment in whichthe average relative humidity of the compartment air is maintained at avalue sufliciently high to properly preserve exposed foodstuffs, withoutdehydration. However, in refrigerators embodying such high humiditycompartments, it has provendiflicult to insure the desired degree ofcompartment humidity throughout the varying seasons of the year, whilestill preventing the moisture-content from reaching undesirably highvalues at certain times. This difficulty may arise under variousoperating conditions, but be comes particularly troublesome in more dampclimates. As is well known, excessive box humidity results inundesirable condensation upon the walls of the compartment. The primaryreason for this will be more apparent hereinafter when further referenceis made to prior construction, but it is to be understood that it hasbecome common to effect cooling of the moist-cold compartment throughits walls and, as a consequence, such walls frequently assumetemperature values below the dew-point temperature of the compartmentair, when the relative humidity in the compartment has reached theundesirably high Values mentioned. above.

It is a primary object of the present invention to provide an improvedrefrigerator incorporating humidity control apparatus which is not onlyhighly effective, but is characterized by unusual simplicity and lowcost.

More particularly, my invention has as an object the provision of arefrigerator of the aforesaid moist-cold type, in which the maximumrelative humidity of the compartment air may be positively limited to apredetermined value below 100%, whereby to prevent the undesiredaccumulation of moisture upon the walls of said compartment.

In accordance with one embodiment of the invention, it is also an objectto provide humidity control apparatus of such a character as to ob viatethe necessity for humidity-responsive switching devices, blowers, andlike apparatus.

The present invention further contemplates the provision of arefrigerator including an air dehumidifying zone which, while effectiveto prevent excessively high compartment humidity, may

be utilized under temperature conditions such as to completely eliminatethe possibility of frost accumulation in said zone, if such operation isdesired.

To the above general ends, and in the broad aspect, my inventioncontemplates locating within the food storage compartment a portion ofthat relatively high temperature evaporator which cools the walls ofsaid compartment, and utilizing said portion to effect condensation andconsequent removal of excess moisture from the compartment air. Whilethis evaporator may form a part of a refrigerating system of any desiredtype, I prefer to employ a secondary refrigeration system secured in theusual convoluted arrangement about the exterior walls of the foodcompartment inner liner, one or more passes" of tubing being arrangedwithin said compartment, as aforesaid.

The invention extends further to certain novel and advantageousconstructional features and arrangements hereinafter described, andillus-- trated in the accompanying drawings, in which:

Figure 1 is a view in perspective of a refrigerator embodying theinvention;

Figure 2 is a view similar to Figure l, and illustrating a modified formof the present invention;

Figure 3 is an enlarged sectional view taken in the direction indicatedby line 3-3 of Figure 2; and

Figure 4 is an enlarged sectional view taken through the verticalmid-plane of a portion of the apparatus shown in Figure 2 and in thedirection indicated by line 4-4, applied to Figure 3.

First making detailed reference to Figure 1, there is shown arefrigerator which includes an outer shell 2 and an inner shell or linermember 3 defining a so-called moist-cold food storage compartment 4,which compartment may be fitted with a plurality of shelves of anydesired type. The cabinet would, of course, be provided with a door (notshown) said door being adapted to seat thereagainst in the plane definedby vertical and horizontal breaker-strips 5 and 6, respectively. In theembodiment illustrated, the refrigerator further includes ice-freezingand low-temperature storage compartments to which access may be hadthrough doors shown at 1'l. It will be understood that the compartment 4is thermally isolated from the low-temperature storage sec-. tions(which, per se, need not be further described) in order that it may bepossible to operate compartment 4 at relatively high temperatures ascompared with the temperature of said sections, such isolation alsoserving to prevent said compartment 4.

'iently be accomplished by the use of a double 3 the undesiredfrosting-out of moisture present in These ends may conventhicknesspartition of glass or some other suitable insulating material. T hispartition is shown at 8 and appears to best advantage in Figure 4.

Although the refrigerant circuits may take any one of several forms,there is illustrated an arrangement in which the main compartment 4 iscooled by means of refrigerant tubing 9 secured in convolutedarrangement about the exterior side and rear surfaces of the inner linerand, as shown, constituting the evaporator portion of a secondaryrefrigerant circuit of known type. It will be appreciated that thistubing 9 is located within the insulation M which fills the spacebetween the outer shell and inner liner.

' in the circuit utilized to refrigerate the storage sections aforesaidand, as fragmentarlly illustrated in Figure 1, said evaporator is fed bya liquid line l3 extending upwardly from the vicinity of saidlow-temperature storage sections, a portion of the suction linereturning to the main condensing unit (not shown) being illustrated atH. heat exchange association is well known, further and more detaileddescription is unnecessary.

As thus far described, the structure corresponds substantially to thatcommonly utilized in multi-temperature refrigerators and is designed;for example, to maintain the surface of said liner 3, definingthe-compartment 4, at a temperature of approximately 38 F. There is, ofcourse, a gradient between this temperature and the temperature of thetubing 9, the value of which will be dependent upon certain designfactors, including the length of tubing convoluted about the liner. aswell as the thickness of the said liner and the nature of theprimarysecondary connection. In the embodiment illustrated, thetemperature of the tubing 9 may be in the neighborhood of 34 F.

It should be borne in mind that the invention is concerned with theelimination of excessive moisture from the air within the compartment l,primarily to prevent the undesired deposition of condensate on the wallsof the inner liner through which walls the compartment 4 isrefrigerated.

As such primary-secondary.

4 through the walls of the compartment by arranging an evaporator inthermal transfer relation therewith. In such constructions, ,as

brought out above, the compartment walls being g cooler than the airwithin said compartment were subject to accumulation of an undesirablecoating of moisture, whenever the relative humidity of the air had risensubstantially. Various arrangements for eliminating this difficulty havebeen devised, some of which are effective and advantageous.

As far as I am aware, however, it has not been previously recognizedthat the problem is susceptible of extremely simple solution by locatinga small portion of the evaporator system directly within the spacedefined by the cooled walls.

In the apparatus illustrated in Figure 1, provision is made for theeffective removal of undesired moisture in this novel and unusuallysimple manner, as will now appear.

After the secondary refrigerant has been returned to the liquid phase inthe condenser II,

it is delivered downwardly through a section of as tubing 90, whichtubing is arranged within the food compartment 4, and is exposed to thecirculating air therein. As pointed out hereinafter, some of the liquidrefrigerant is volatilized in section 9a. At the point of introductioninto 30 the food space, the tubing passes through a mounting grommet l5,while the lower extremity of the section 80. passes through an aperturel6 provided in the partition 8. From this point, as will be clear fromthe drawing, liquid refrigerant is delivered to the convoluted passages9 within which the volatilization is completed.

The secondary circuit is closed by re-introduction of the vaporizedrefrigerant, into the condensing header l2, as indicated at H. In orderto promote the free circulation of air about the tubing portion So, fora purpose which will become apparent hereinafter, said portionpreferably extends along the wall of the liner in spaced relationthereto. 7

In view of the fact that the secondary system constitutes a singleclosed circuit, all portions of which are at substantially the samepressure,

tubing portion So will 'be maintained at substanis preferably maintainedsubstantially constant.

the exposed portion always being somewhat cooler than the wall surfaces,a 4 differential having been given by way of example. As a result ofthis temperature differential, the area immediately surrounding saidportion So, will be maintained at a low vapor pressure, with respect tothe vapor pressure existing in the vicinity of the higher temperaturewalls. Consequently, the moisture present within the compartment 4 willbe deposited upon the.exposed secondary tubing, rather than upon therefrigerator walls, such deposition taking place whenever the relativehumidity of the box air has risen to such a pointthat contact of said,air'with the cooler tubing reduces the temperature of the air below thedew-point. As shown in Figure 1, the tubing 8a is provided with 75 a fluI8 to faciliate the transfer of latent heat necessary to efiect themoisture condensation and, as mentioned above, the tube is spacedslightly from the liner wall to increase contact of the airtherewith.The moisture condensed passes downwardly along the exterior surface ofthe tubing and is delivered to the passage I!) through which it may beremoved from the refrigerator.

'It will be evident that the apparatus of the present invention willeffectively prevent any undesirable accumulation of condensate upon thewalls of the inner liner. Although moisture, when first introduced, maytend to deposit upon the wall surfaces, a stabilized condition isreached quickly when the main door is closed, and any small amounts ofmoisture so deposited will then migrate to and be deposited upon thetube So, as a'result of the above mentioned vapor pressure differential.

There is no possibility of reducing the moisture content of the box airbelow a predetermined value of percent relative humidity, provided theproper temperature relations are maintained. The reason for this will beunderstood'by refer ence to a psychrometric chart, from which it will beclear that operation of the tube portion 9a at 34 F. could not reducethe percent relative humidity of box air at, for example, 40 F. to avalue below 80%. Below such a percentage, under the temperatureconditions assumed for exemplary purposes, the air in the vicinity ofthe exposed tubing would not be reduced below the dew-point temperature,and no moisture removal will take place. Tests have indicated that thesystem as thus far described is unusually effective in preventingundesirable increases of box humidity and consequent moisture collectionupon the interior walls.

While it is preferred that the secondary system be operated at atemperature slightly above freezing, to prevent the accumulation offrost upon the moisture-condensing portion 8a, other modes of operationmay be followed, if desired. A reduction of the secondary temperature toa value slightly below freezing results in a. somewhat more rapidresponse to the introduction into the box of unusually high quantitiesof free moisture and, for this reason, operation at sub-freezingtemperatures may be desirable under certain conditions.

For best operational results, it has been found desirable to stabilizethe temperature of the secondary system to a degree greater than thatpossible with the system as thus far described. and for this purpose avalve responsive to the vapor pressure within the secondary tubing maybe employed. Such a valve is indicated at 20 in the drawings, and iswell known in this art. If

the refrigerating capacity of the primary system is very high, or theprimary temperature fluctuates considerably, undesirable temperaturefluctuations may be reflected in the secondary systern. In addition toovercoming this disadvantage, a valve responsive to the secondarypressure has a tendency to insure unidirectional flow of the refrigerantthrough the secondary system, thereby increasing the capacity of thesystem.

There has been illustrated in Figures 2 to 4 a second embodiment of theinvention, which while essentially similar to that already described, isparticularly well adapted for use in extremely humid climates, or whenvery frequent access is had to the refrigerator. Under such conditions,it may be desirable to accelerate the response of the moisture controlapparatus.

In this second embodiment, the refrigerator and the associated primaryand secondary systems are similar to those already described and,accordingly, further description of those portions will be omitted inthe following description.

This form of the invention, is concerned with an arrangement in whichundesired humidity in the main food storage compartment is eliminated byeffecting periodic circulation of the compartment air through a ductsurrounding the secondary tubing 9a, and thereby in heat exchangerelation with said tubing. In this system, the transfer of latent heatfrom the moisture laden air and consequent moisture condensation may beeffected very rapidly when the need for moisture removal arises.

In the apparatus depicted in Figures 2 to 4 this air circulation iseffected, as and when required, by means of a motor 2! and an associatedblower 22, operable periodically in response to the humidity conditionsexisting in-the compartment 4, as will be set forth in detailhereinafter. As shown at 23 in the drawings, the rear wall of the innerliner is provided with an aperture in registry with the inflow portionof blower 22, said blower being mounted upon the exterior surface of theliner in any convenient manner. The outflow passage 24 extendshorizontally across the back of the liner, and is provided with anopening in registry with an outflow aperture 25 formed in the liner wallimmediately above the secondary portion 9a. A cap member 28 directs theair downwardly through the duct 2] surrounding the moisture condensingtube, said duct being provided with outwardly extending flanges 28--28adapted to be resiliently'received within the undercut portions of apair of mounting channels 29 fixed to the inner wall of the liner (seeFigure 3). As shown at 30, the lower portion of the duct 21 communicateswith a generally C-shaped air injection duct'3l extending about the sideand rear walls of the liner 3, directly above the insulating partition8. This duct is provided with a plurality of apertures 32 to permitpassage of air from said duct and reinjection into the food compartment4. As designated by arrows appearing in the drawings it will be apparentthat air is initially withdrawn from the compartment through aperture23, passes through the blower out-flow passage 24 and thence downwardlythrough duct 21 in heat exchange association with the tubing 9a. Thecircuit is, of course, completed by reinjection of the air intocompartment 4 through apertures 32, as above described.

This controlled circulation may conveniently be initiated by means of ahumidostat 33 which, while it may be of any desired type, is preferablyof the type disclosed and claimed in the copending application of JohnJ. Bauman, Serial No. 537,701, filed May 2'7, 1944. Description of thehumidostat is unnecessary herein, beyond mentioning that it is adaptedto initiate operation of the motor 2| when the relative humidity in thecompartment 4 has risen just above a predetermined value. Further, itwill be evident that while humidostat control is preferable, it would bepossible to effect periodic actuation of the air circulation blower byother means. For example, the motor 2| could be energized at periodic,timed intervals, in accordance with the average humidity conditionsencountered in practice in any particular locality. Further, in thebroad aspect, certain advantages of the instant embodiment could berealized by a slow continuous circulation oi. the compartment air underthe influence of the blower 22.

In all essential respects, the operation and advantages of this secondform of the present invention are similar to those already set forth inconnection with the first embodiment. As indicated above, more rapidresponse to excessive humidity conditionsmay be realized with the bloweroperated system. Again, the question of operating temperatures for thesecondary system, and hence for the moisture condensing por-' tion Ia,are determined bythe maximum permissible average relativehumidity valueof the compartment air, and the determination of whether or not somefrost collection on the exposed tube is objectionable.

From the foregoing, it will be evident that the present inventionprovides an extremely simple and eil'ective apparatus for eliminatingexcessive moisture frequently present in refrigerators of the typereferred to. The importance of the resultant prevention :of condensateaccumulations within the box, will be readily appreciated.

I claim:

1. In a refrigerator, a storage compartment, evaporator means adapted tomaintain wall portions of said compartment at a refrigeratingtemperature whereby to cool the compartment, evaporator means withinsaid compartment affording a surface maintained at a temperature lowerthan the temperature at which said wall portions are maintained and uponwhich surface the deposition of moisture is substantially localized,means normally preventing contact of compartment air with said surface,and humidity-responsive means for-eflecting intermittent circulation ofthe compartment air in heat exchange relation with said surface.

2. A construction in accordance with claim 1, wherein said last meansisresponsive to an increase in relative humidity above apredeterminedvalue and is adapted to maintain said circulation until therelative humidity is reduced to said predetermined value.

3. In a refrigerator, 9. storage compartment, evaporator means adaptedto maintain wall portions of said compartment at a refrigeratingtemperature whereby to coolthe compartment, evaporator means within saidcompartment affording a surface maintained at a temperature lower thanthe temperature at which said wallportions are maintained and upon whichsurface the deposition of moisture is substantially localized. a housingnormally preventing contact of compartment air with said surface, ablower located exteriorly of said compartment and having inflow andoutflow passages communicating with said compartment and said housing,respectively, and means for initiating operation of said blower inresponse to an increase in relative humidity above a predeterminedvalue, whereby to effect circulation of the compartment air in heatexchange relationwith said surface.

4. In a refrigerator, a storage compartment, a relatively largerefrigerant evaporator arranged in high heat transfer relation withexterior surfaces of the walls of said compartment and effective tomaintain interior wall portions at a temperature higher than thetemperature of said exterior surfaces, and a relatively smallrefrigerant evaporator within said compartment, both said evaporatorsbeing maintained at substantially the same pressure to insure that saidsecond-mentioned evaporator will be maintained .vailing in saidfirst-mentioned evaporator and somewhat 'lower than the temperatureofsaid interior wall portions. e

5. In a refrigerator, a storage compartment, a relatively largerefrigerant evaporator arranged in high heat transfer relation withexterior surbe maintained at a temperature substantially equal to thatprevailing in' said first-mentioned evaporator and somewhat lower thanthe temperature 'of said interior wall portions.

6. In a refrigerator, a high humidity storage compartment, cooling meansfor said compartment, said cooling means having relatively large heatexchange capacity and being effective to cool the compartment air bymaintaining exposed surfaces within said compartment at a predeterminedtemperature somewhat above the freezing point of water and below that ofthe air within' said compartment whereby, under high humidityconditions, said exposed surfaces are subject to undesirable moisturecondensation thereon, and means forpreventing such condensation withoutreducing the moisture content of the compartment air below a desiredpredetermined lower value of percent relative humidity, said meanscomprising; a relatively small cooling element located within thecompartment and maintained at a temperature slightly below thetemperature of said exposed cooling surfaces, means normally preventingcontact of compartment air with said element, and means for effectingintermittant circulation of the compartment air in heat exchangerelation with said element.

"I. In a refrigerator, a metallic liner defining a refrigerated space,and a refrigerant evaporator comprisin tubing the major portion of whichextends about exterior wall surfaces of said liner in high heat exchangerelation therewith, whereby to refrigerate said space through the wallsof said liner, a minor portion of said evaporator tubing being disposedin said space, said evaporator tubing being at substantially the sametemperature throughout, and the temperature gradient through said cooledwalls being such that interior surfaces of said cooled walls aremaintained at a temperature slightly higher than the temperature of saidminor portion.

8. In a refrigerator, a liner defining a refrigerated space, and arefrigerant evaporator comprising tubing the major portion of whichextends about exterior wall surfaces of said liner in 'high heatexchange relation therewith, whereby to refrigerate said space throughthe walls of said liner, a minor portion of said evaporator tubing beingdisposed within said space along an interior wall surface of the linerand constituting a condensate-localizing surface,

9. In a refrigerator, a liner defining a refrigerated space, arefrigerant evaporator comprising tubing the major portion of whichextends about exterior wall surfaces of said liner in high heat exchangerelation therewith, whereby to refrigerate said space through the wallsof said liner, a minor portion of said evaporator tubing being disposedwithin said space along an interior wall at a temperature substantiallyequal to that pre- '76 surface of the liner and constituting a conden- 9sate-localizing surface, and means providing for removal of condensatefrom'saidrefrigerated space. V v

10. In a refrigerator, a high humidity storage compartment, coolingmeans arranged in heat exchange relation with exterior surfaces of thewalls of said, compartment. saidcooling means having relatively largeheat exchange capacity being effective to cool the compartment air bymaintaining exposed surfaces within said compertinent at a predeterminedtemperature somewhat above the freezing point of water and below that ofthe air within said compartment whereby, under high humimty conditions,said exposed surfaces are subject to undesirable moisture condensationthereon, and means for preventing such eondensation without reducing themoisture small cooling element content of the compartment air below adesired predetermined lower value of percent relative humidity, saidmeans comprising a relatively REFERENCES CITED The following referencesare of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,133,958 Kalischer Oct. 25, 19382,261,681 Ullstrand Nov. 4, 1941 2,292,015 Schweller Aug. 4, 19422,361,792 Philipp Oct. 31, 1944 2,370,267 Starr Feb. 27, 1945

